The invention relates to a drive mechanism for an electrical switchgear apparatus, in particular for an electrical circuit breaker.
In the document FR 2,589,626 a drive mechanism of the contacts of an electrical circuit breaker is described comprising an energy storage sub-assembly and an opening and closing sub-assembly. The energy storage sub-assembly comprises an energy storage spring associated to the movable contact in such a way that relaxation of the energy storage spring drives the movable contact to its closed position, and a closing latch designed to latch the energy storage spring in a loaded state. The opening and closing sub-assembly comprises an opening spring and an opening latch designed to latch the opening spring in a loaded state. The opening spring is associated to the movable contact in such a way that relaxation of the opening spring drives the movable contact to an open position and that movement of the movable contact to its closed position causes loading of the opening spring. In the closed position, the movable contact is latched in position by the opening and closing sub-assembly controlled by the opening latch. The energy storage sub-assembly is then uncoupled from the contacts so that it is possible to move the energy storage spring to its loaded state by means of a manual or motorized drive mechanism, whereas the switchgear apparatus remains closed, and then to keep the energy storage spring in the loaded position by means of the closing latch. From this apparatus closed, energy storage sub-assembly loaded position, a contact opening, contact closing, contact re-opening (OCO) sequence can be executed without having to perform an intermediate reloading sequence, by successively commanding unlatching of the opening latch, unlatching of the closing latch, and then unlatching of the opening latch again.
In order to be able to fit the energy storage spring simply, the control sub-assembly is equipped with a removable telescopic means wherein the energy storage spring is inserted, and with a cotter-pin enabling the telescopic means and the spring to be locked in a compressed position thus allowing the telescopic means and the spring chosen to be fitted and removed as a single part. A whole range of different closing springs can thus be provided, corresponding to different closing energies, able to be fitted on the same telescopic means, which enables a whole switchgear range to be achieved from a single standard mechanism.
The choice of the energy storage spring does however remain limited by the space available in the mechanism for the spring. When the energy of the mechanism is to be increased beyond what is allowed by the available space, a new mechanism has to be created deduced from the previous one by homothetic transformation.
To increase the power available, it can naturally also be envisaged to abut two identical mechanisms. However such a solution assumes that two operating mechanisms coexist, which gives rise to coordination problems, in particular as far as the opening latches and closing latches are concerned. In addition, among the duplicated parts, many of them are of no use.
In the document FR 2,683,089, it has been proposed to couple to a standard main drive mechanism able to drive on its own the three poles of a three-phase circuit breaker, an auxiliary mechanism dedicated to a fourth pole, so as to constitute a four-pole assembly. The contacts of the auxiliary pole are coupled to a rotary switching bar by means of contact pressure springs. The auxiliary mechanism comprises an auxiliary spring which, in the closed position of the bar, exerts a torque on the bar opposing the torque resulting from the contact pressure springs. The auxiliary spring only acts on the bar when the latter is positioned between an intermediate load take-up position and the closed position, these two positions being close to one another. On the other hand, when the bar is between the open position and the intermediate loading position, the auxiliary spring no longer acts on the bar. Such a mechanism provides a solution when the contact pressure exerted on the contact fingers has to be increased. It does not on the other hand enable the force exerted at the beginning of closing, that conditions the initial power and acceleration of the mechanism and the time required to perform the closing operation, to be increased.
The object of the invention is therefore to remedy the shortcomings of the state of the art so as to increase the closing energy of a circuit breaker mechanism while reducing the modifications of the existing mechanism to the minimum.
According to the invention, this problem is solved by means of a closing assistance mechanism for an electrical switchgear apparatus, comprising:
a switching shaft movable in rotation in a closing direction from an open position to a closed position, and in an opening direction opposite to the closing direction, from the closed position to the open position;
a closing assistance spring, movable between an unloaded position and a loaded position;
a loading shaft movable in rotation in a loading direction;
loading means associated to the loading shaft to drive the closing assistance spring from the unloaded position to the loaded position when the loading shaft rotates in the loading direction to a ready to close position and to release the closing assistance spring when the loading shaft goes beyond the ready to close position in the loading direction;
transmission and coupling means comprising:
a driving coupling means in permanent kinematic connection with the closing assistance spring,
a driven coupling means securedly affixed to the switching shaft, the driven coupling means following a rotary trajectory in the closing direction when the switching shaft moves from the open position to the closed position, and in the opening direction when the switching shaft moves from the closed position to the open position;
a return means of the driving coupling means;
the transmission and coupling means being such that:
when the switching shaft is in the open position and the closing assistance spring is in the loaded position, the driving coupling means is in a load takeup position, engaged with the driven coupling means;
when the closing assistance spring moves from the loaded position to the unloaded position, the driving coupling means drives the driven coupling means to an intermediate uncoupled position, and the switching shaft moves from the open position to an intermediate uncoupled position in the closing direction;
when the switching shaft moves from the uncoupled position to the closed position in the closing direction, the driving coupling means is driven to a withdrawn position by the return means and the driven coupling means is uncoupled from the driving coupling means;
when the closing assistance spring moves from the unloaded position to the loaded position, the driving coupling means moves from the withdrawn position to the load take-up position following a trajectory not interfering with the rotary trajectory of the driven coupling means.
The closing assistance mechanism is very simple since it comprises neither a closing latch nor an opening latch, operation thereof being achieved by rotation of the loading shaft. The closing assistance spring enables at least a part of the energy required for closing to be communicated to the switching shaft.
Advantageously, the loading means and the transmission and coupling means have in common a multifunctional lever pivoting between a loaded position and an unloaded position around a fixed geometric axis, operating in conjunction with a loading cam securedly affixed to the loading shaft, with the closing assistance spring, and with the driving means in such a way that:
when the multifunctional lever pivots from the unloaded position to the loaded position due to the bias of the loading cam when rotation of the loading shaft takes place, the multifunctional lever drives the closing assistance spring from the unloaded position to the loaded position and drives the driving means from the withdrawn position to the load take-up position;
when the multifunctional lever pivots from the loaded position to the unloaded position due to the bias of the closing assistance spring moving from the loaded position to the unloaded position, the multifunctional lever drives the driving means from the load take-up position to the intermediate uncoupled position.
The multifunctional lever enables the mechanism to be achieved with few parts.
According to one embodiment, a first of the driving and driven coupling means comprise a pin, and a second of the driving and driven coupling means comprise a hook having a shape such that:
when the switching shaft is between the open position and the uncoupled position, the pin is held by the hook and,
when the switching shaft goes past the uncoupled position in the closing direction, the pin escapes from the hook due to the bias of the return means.
Coupling is then achieved in a particularly simple and rugged manner. Other coupling means can naturally be envisaged.
Preferably the return means comprise a return spring.
According to one embodiment, the transmission and coupling means comprise in addition: a coupling cam securedly affixed to the loading shaft, operating in conjunction with the driving coupling means when the driving coupling means move from the withdrawn position to the load take-up position.
The invention also relates to a drive mechanism associating a main mechanism controlled by a closing latch and an opening latch, with a closing assistance mechanism as described previously. The main mechanism comprises an energy storage spring which alone has to provide at least the energy necessary to drive the switching shaft from the intermediate uncoupled position to the closed position.